1. Field of the Invention
The present invention relates to image display apparatuses that change the size of an observed image in accordance with the movement of the head of the observer, and display an appearance image of an image shooting apparatus on an image shot by the image shooting apparatus.
2. Description of the Prior Art
Recent years have seen gradual spread of such display apparatuses that, by changing the displayed image in accordance with the view direction of the image observer, provide the observer with a sense of realism to such an extent that the observer feels as though he were put in the displayed image. For example, Japanese Laid-Open Patent No. H3-56923 discloses how, in a stereoscopy apparatus that displays images taken with a stereoscopic camera on a head-mounted display (hereinafter referred to as HMD), images are displayed in accordance with the direction of the observer's head by controlling the shooting direction of the stereoscopic camera to correspond to the direction of the HMD. Using a stereoscopic apparatus of this type, the observer can observe the image in a desired direction by simply changing the direction of his/her head.
However, in the stereoscopy apparatus described above, although the area of the image displayed on the HMD is changed in accordance with the shooting direction, the size of the displayed image cannot be changed as the user desires.
It is possible to make the shooting area variable on the stereoscopy apparatus described above by equipping it with a camera having a zoom lens. In that case, however, if the focal length of the zoom lens is controlled manually as in conventional cameras, the person wearing the HMD needs to be near the camera all the time. This greatly harms conveniences that the HMD offers in portability and operability.
On the other hand, a camera apparatus is known which is moved around by remote control in order to change the shooting position. An operator of such a camera apparatus controls movements of the camera while observing images taken by the camera. This type of camera is useful in shooting, for example, in places that are dangerous or inaccessible to human beings, because it can be controlled from a remote place to perform shooting.
However, with a conventional mobile camera apparatus, since it can only display images taken by the camera, the operator cannot correctly recognize the size of the camera itself, which often results in troubles in movement control. For example, in a situation where there is an obstacle ahead in the movement direction, it is difficult to judge to what extent the camera should be moved rightward or leftward in order to avoid the obstacle. Wrong judgement may cause the camera to collide with the obstacle with damage given to the camera. In a situation where there are obstacles on both sides of the path along which the camera will be driven, wrong recognition of the width of the path with respect to that of the camera may cause the camera to be trapped by the obstacles, making it impossible to move the camera forward nor backward.
If a mobile camera apparatus is provided with a function for making the shooting direction follow the direction of the observer's head, it is possible to shoot in any direction irrespective of the movement direction of the camera, enhancing its utility greatly. In this case, however, the image taken and displayed does not correspond to the movement direction of the camera, making the movement control operation more difficult.